Field of the Invention
This invention relates to a scanning device and more particularly to a scanning device which is capable of providing a linear scanning line even if a stationary beam is caused to impinge upon a deflecting mirror surface disposed parallel to the rotation axis of the deflecting mirror, from a finite angle with respect to a plane crossing both the rotation axis and the deflecting mirror at right angles therewith.
When a stationary beam is caused to impinge upon a deflecting mirror surface disposed parallel to the rotation axis of the deflecting mirror, from a finite angle with respect to a plane crossing both the rotation axis and the deflecting mirror at right angles therewith--this will hereinafter be referred to the case where the stationary beam is caused to impinge obliquely--the path of the scanning beam from the deflecting mirror surface assumes a conical shape with the point of incidence of the stationary beam as the vertex. Accordingly, the scanning line formed by such scanning beam is not linear. As the deflector having a deflecting mirror surface parallel to the rotation axis, there is known a rotatable polygonal mirror, a galvano-mirror or the like.